Certain communication protocols only provide a login authentication dialog on accessing a particular resource, and do not provide a logout or de-authentication method to remove authentication. For such protocols, once a user is authenticated, the user remains authenticated. This restricts the ability to allow multiple users to share a common access point utilizing such a limited protocol.
A well-known protocol having this authentication limitation is HTTP. HTTP provides a basic authentication scheme, in which a web page designer may assign user name/password pairs to particular web resources. One typical technique for triggering authentication dialog boxes is through use of the .htaccess and .htpasswd files utilized by Apache web severs (well-known public-domain Web servers). When a user attempts to access a protected resource, such as with a web browser, the htaccess file tells the web server to instruct the user's browser to display an authentication dialog comprising a user name and password field. The user must then supply credentials that match the .htpasswd file. If the user provides proper credentials, the user is then allowed access to the resource.
Unfortunately, HTTP fails to provide a de-authentication ability for a web browser session. That is, one cannot secure a web site with HTTP basic authentication, and then let multiple users access the site with a single web browser running on a public terminal. This configuration fails because, under basic HTTP authentication, once a first user is authenticated, then the browser session remains authenticated until the web browser session, e.g., the browser window, is closed. This limitation has resulted in having to provide HTTP extensions for logging users into and out of web resources, e.g., by way of Common Gateway Interface (CGI) scripts, Java applets, etc.
This limitation may also preclude use of HTTP basic authentication in circumstances where a browser session cannot be closed. For example, terminals having a web browser embedded in Read Only Memory (ROM), or browsers that are integrated into an operating system, may lack a provision for being restarted, and therefore require rebooting or powering cycling to de-authenticate a browser's session.